Chip removing or cutting tools of the type generally mentioned above are used for the machining of workpieces of metal and other non-fibrous materials, such as composites. The basic bodies of the tools are usually manufactured from steel, while the replaceable cutting inserts are manufactured from cemented carbide or other materials having greater hardness and resistance to wear than steel.
Partly as a consequence of cemented carbide being a comparatively costly material, there is among tool manufacturers an aim to construct the cutting inserts with as many cutting edges as possible per unit volume of cemented carbide. This has resulted in so-called double-sided cutting inserts and cutting inserts having multiple cutting tips, respectively, each of which may be double-sided, i.e., have cutting edges along an upper side as well as an under side. Examples of the last-mentioned type of cutting inserts are disclosed in US 20100329800 and SE 533249, the first-mentioned document of which describes a cutting insert intended for turning having three alternately usable, double-sided cutting tips, and the last-mentioned a cutting insert intended for milling having not less than eight, double-sided cutting tips.
A disadvantage or limitation of previously known cutting inserts having a plurality of cutting tips and many cutting edges, is, however, that all cutting tips are located in one and the same plane, indexing of the cutting insert being carried out by step-wise turning forward the cutting tips in said plane. This means that the cutting inserts cannot be used for certain types of machining operations, e.g., turning of shoulder or shoulder milling. Thus, the cutting insert according to SE 533249 is formed with a disc-shaped or pulley-like core, along the periphery of which eight diminutive, double-sided cutting tips are located at a pitch of 45°. It is true that this design allows face milling (at moderate cutting depths), but not shoulder milling, which requires that the cutting insert as well as a behind part of the tool basic body is contained within a sector or corner angle of at most 90°.
The turning insert according to US 20100329800 includes three double-sided cutting tips that protrude radially from a hub-like, central core. Because a sector, which is defined by the angle between the nose edge of an individual cutting tip and the nose edges of the two other cutting tips, amounts to 60°, this cutting insert may very well be used for turning of shoulder. However, then, the number of cutting tips is limited to exactly three, i.e., to in total 3×2=6 usable cutting edges. Each hypothetical attempt to further increase the number of cutting edges by providing the cutting insert with additional cutting tips in one and the same plane would, however, entail an increase of the sector angle to 90°, and thereby make impossible the use of the cutting insert for turning of shoulder.